Carburetor



y 30, 1967 D. D. STOLTMAN 3,322,408

CARBUR ETOR Filed Sept. 1, 1965 2 Sheets-Sheet 1 INVENTOR.

parted/a a0. Sb/fmazz United States Patent 3,322,408 CARBURETOR Donald D. Stoltman, Henrietta, N.Y., assignor to General Motors Corporation, Delaware Filed Sept. 1, 1965, Ser. No. 484,267 7 Claims. (Cl. 261-44) This invention relates to carburetors for internal combustion engines and is particularly directed to a carburetor of the air valve type.

An air valve carburetor is uniquely capable of providing an air-fuel mixture which may be closely tailored to the requirements of the engine throughout a wide range of engine air flow rates. In such a carburetor, a flow responsive valve located in the air inlet is positioned by air flow to the engine; this air valve thus regulates and meters the engine air flow. Fuel metering rods are in turn positioned by the air valve so that fuel flow to the engine is metered in desired proportions to the air flow. Since direct control is exerted over both air and fuel flow to the engine, this type of carburetor very accurately regulates the proportions of the air-fuel mixture delivered to the engine.

Until recently air valve carburetors have not achieved a significant degree of commercial success. This may be attributed to, among other reasons, the fact that no available air valve carburetors had the air and fuel metering controls both compactly and conveniently located. This invention provides an air valve carburetor in which these controls are located so that fuel is metered as it is delivered into the air stream in the center of the mixture conduit. The controls are thus readily accessible for servicing and yet are located so that a proper distribution of the air-fuel mixture may be formed in the mixture conduit.

The details as well as other this invention are disclosed in and in the drawings in which:

FIGURE 1 is an elevational view of the carburetor mounted upon an engine;

FIGURE 2 is a sectional view of the carburetor along line 22 of FIGURE 1 and illustrates the configuration and location of the air valve;

FIGURE 3 is a sectional view along line 3-3 of FIGURE 2 illustrating the economy metering system of this carburetor; and

FIGURE 4 is a sectional view along line 44 of FIGURE 1 illustrating the power metering system of this carburetor.

Referring to the drawing, a carburetor 10 is secured to the intake manifold 12 of an internal combustion engine. A single mixture conduit 14 extends through the carburetor and is controlled at the outlet end by a throttle valve 16 secured to a throttle valve shaft 18.

A choke valve 20 is disposed in the inlet to mixture conduit 14 and is controlled in the conventional manner by a thermostatic member (not shown) and a vacuum break mechanism 22. As illustrated in FIGURES 3 and 4, the vacuum break mechanism 22 includes a diaphragm 24 subjected on its right-hand side to manifold vacuum through a passage 26 which communicates with mixture conduit 14 below throttle valve 16. Before the engine is started, choke valve 20 will be closed by the thermostatic element. However, as soon as the engine begins to run under its own power, diaphragm 24 will be pulled to the right and a plunger 28 secured thereto will pull choke valve 20 to a slightly open position to lean the mixture.

As shown in FIGURE 1, a lever 30 secured to choke valve shaft 32 vertically positions a link 34 which in objects and advantages of the following description Detroit, Mich., a corporation of turn positions a fast idle cam 36. A throttle lever 38 secured to throttle shaft 18 carries an idle adjusting screw 40 which cooperates with fast idle cam 36 in the customary manner to regulate the throttle position during warm-up of the engine.

As shown in FIGURES 2 through 4, an air valve 42 is pivotally disposed in mixture conduit 14 upon an air valve shaft 44 which extends through the walls of mixture conduit 14. A U-shaped lever 46 is secured at both ends to the ends of air valve shaft 44 and extends about the exterior of the carburetor. As shown in FIGURES 3 and 4, lever 46 includes arms 48 (one being located on each end of lever 46). A U-shaped link 50 is connected at both ends to arms 48 and extends about the exterior of the carburetor to be secured to a flexible diaphragm member 52. The exterior of diaphragm 52 is acted upon by atmospheric pressure while the other side of diaphragm 52 is subjected to the pressure in the chamber 54 enclosed thereby. Atmospheric pressure operates on diaphragm 52 in an air valve opening direction and is opposed by the bias of a spring 56 within chamber 54. Chamber 54 is subjected through a passage 58 to the pressure in mixture conduit 14 at a location between air valve 42 and throttle valve 16.

As throttle valve 16 opens, the vacuum existing therebelow is applied against the downstream side of air valve 42 and against diaphragm member 52. Diaphragm 52 is pulled to the right and, through link 50 and arms 48, rotates air valve shaft 44 in a counterclockiwse direction. Air valve 42 is thus opened and admits air to reduce the vacuum therebelow. Diaphragm 52 and spring 56 cooperate to maintain the vacuum below air valve 42 Within a predetermined range.

As shown in FIGURES l, 3 and 4, a link 60 is positioned in a slot 62 in throttle lever 38 and extends through an opening in the U-shaped lever 46. A spring 64 is compressed about link 60 between lever 46 and a shoulder 66 formed on link 60. As throttle valve 18 is brought to a wide open position, link 60 will be forced upwardly by the end of slot 62. Spring 64 then urges the U-shaped lever 46 in a counterclockwise, or air valve opening, direction. Thus air valve 44 will be urged open Whenever the throttle 16 is opened suddenly, thereby increasing air flow through mixture conduit 14.

As best shown in FIGURE 3, an adjustable stop 68 is carried by U-shaped lever 46 to cooperate with an abutment 70, limiting air valve closing movement. Stop 68 allows accurate adjustment of the closed or idling position of air valve 42 and, in addition, yields to absorb impact should a backfire type of explosion occur in the intake manifold, thereby permitting air valve 42 to contact the wall of mixture conduit 14 and avoid distortion of the air valve.

Referring to FIGURE 3, a fuel bowl 72 includes a conventional float mechanism 74 for maintaining the fuel at a substantially constant level. A tube 76 extends from the bottom of fuel bowl 72 to a metering passage 78 in a fuel nozzle 80 projecting into mixture conduit 14. A passage 82 connects the upper portion of fuel bowl 72 with the inlet of mixture conduit 14 so that the pressure on the fuel surface is maintained at substantially atmospheric pressure. The discharge outlet of metering passage 78 is centered over throttle valve 16 in the subatmospheric pressure region created by air valve 42. The pressure differential across the fuel in bowl 72 caused by atmospheric pressure on the surface and subatmospheric pressure at the outlet of nozzle 80 causes fuel to flow from the bowl 72 into mixture conduit 14.

An economy metering orifice 84 is disposed at the discharge outlet of metering passage 78 and is regulated by an economy metering rod 86. Metering rod 86 is supported and positioned by a metering rod carrier 88 secured to air valve shaft 44. As air valve 42 opens, metering rod carrier 88 withdraws metering rod 86 from orifice 84 to permit an increase in the fuel discharge from metering passage 78. This arrangement provides an air-fuel mixture which is closely tailored to the engine requirements throughout the wide range of air flow rates.

Referring to FIGURE 4, a second tube 90 extends from the bottom of fuel bowl 72 to a second metering passage 92 in fuel nozzle 80. A power metering orifice 94 is disposed at the discharge outlet of metering passage 92 and is regulated by a power metering rod 96. Metering rod 96 is also supported and positioned by the metering rod carrier 88 which is secured to air valve shaft 44. As air valve 42 opens, metering rod carrier 88 withdraws metering rod 96 from orifice 94 to permit an increase in the volume of fuel discharged from metering passage 92. Fuel flow through this power metering system is controlled by a manifold vacuum responsive piston 98 so that a power mixture is delivered only when the manifold vacuum is low, indicating the engines requirement for an enriched mixture. Piston 98 is biased by a spring 100 against the force of vacuum applied through a passage from the mixture conduit 14 below throttle 16. The end of piston 98 is formed as a valve 104 which cooperates with a valve seat 106 to prevent air flow from the upper portion of fuel bowl 72 to metering passage 92. When valve 104 is seated on 106, the suction created by air valve 42 is effective to draw fuel from fuel bowl 72 past the power metering orifice 94 and rod 96.

Under higher values of manifold vacuum, piston 98 is drawn toward the left so that valve 104 is unseated from 106. The nearly atmospheric pressure above the fuel in bowl 72 (applied through passage 82 as shown in FIG- URE 3) is then bled through passages 108 and 110, past valve seat 106, to reduce the vacuum in metering passage 92 and prevent or reduce fuel flow through the power metering orifice 94. This arrangement provides a mixture enriched to the precise air-fuel ratios required by the engine.

As shown in FIGURES 2 and 3, an adjusting screw 112 positions metering rod carrier 88 with respect to air valve 42 so that the initial settings of metering rods 86 and 96 with respect to metering orifices 84 and 94 may be accurately determined. This adjustment permits each carburetor to be individually tailored and set to the flow characteristics required by the engine.

As best shown in FIGURE 2, the edge of metering valve 42 has a recess 114 adjacent economy metering rod 86 and economy metering orifice 84. This recess 114 permits a flow of air past the economy metering rod to pro vide air flow when the engine is idling. Similarly, the downstream edge of throttle valve 16, located beneath economy metering rod 86 and orifice 84, has been fiattened as indicated at 116 to permit a flow of idling air. This fiow of air through recess 114 and past edge 116 is mixed with fuel drawn through the economy metering orifice 84 to provide an idling air-fuel mixture. Adjustment of screw and stop 68 permit accurate control over the rate of idle air flow, and adjustment of screw 112 permits variation in the idle fuel flow. This combination allows the idle air-fuel mixture ratio and volume to be precisely determined.

Reviewing the basic configuration of this carburetor, it will be noted that air flow is generally in the downward direction but varies slightly from the vertical in passing the fuel metering orifices. This variation is created by the slight offset of the mixture conduit inlet from the outlet which is greatly advantageous since it permits the fuel metering orifices to be centered over the throttle valve. Such an arrangement promotes a proper distribution of the air-fuel mixture within the mixture conduit.

It should also be noted that the fuel is discharged along the metering rods in a direction slightly depressed from the horizontal. Thus the fuel is discharged at a right angle 4 to the air flow and an even distribution of the fuel throughout the mixture conduit is achieved.

1 claim:

1. An internal combustion engine carburetor comprising a downdraft mixture conduit, a throttle valve pivotally disposed in said mixture conduit and having a recess in the downstream edge thereof to permit flow of an idling air-fuel mixture when said throttle valve is closed, a downwardly inclined fuel delivery nozzle extending into said mixture conduit and having a discharge end centered above said throttle valve, fuel delivery passage means connected to said nozzle to supply fuel thereto, a fuel metering orifice in the discharge end of said nozzle, a metering rod in said mixture conduit associated with said orifice to vary the effective area thereof and control fuel flow therethrough, an air valve pivotally disposed in said mixture conduit, means to position said air valve in accordance with air fiow through said mixture conduit, said air valve being contoured to fit closely about said fuel delivery nozzle and having a recess adjacent said metering orifice to permit flow of idling air when said air valve is closed, and means connecting said metering rod to said air valve to support and position said metering rod whereby fuel fiow is controlled in accordance with air flow.

2. The carburetor of claim 1 which further includes means connecting said air valve and said throttle valve to urge said air valve to a open position as said throttle valve approaches a wide open position.

3. The carburetor of claim 1 which further includes adjustable stop means to prevent closure of said air valve beyond a predetermined position under normal operating conditions.

4. The carburetor of claim 3 wherein said stop means is yieldable to permit further closing movement of said air valve in the event of a backfire through said mixture conduit.

5. An internal combustion engine carburetor comprising 21 downdraft mixture conduit; a throttle valve in said mixture conduit; a fuel delivery system including a fuel bowl, a nozzle extending downwardly into said mixture conduit and having a discharge end centered above said throttle valve, and passage means connecting said nozzle and said fuel bowl; and a metering system including economy and power fuel metering orifices, a metering rod associated with each of said orifices to vary the effective area thereof and control fuel flow therethrough, an air valve rotatably disposed in said mixture conduit to maintain the pressure at the discharge end of said nozzle below the pressure in said fuel bowl during engine operation, means to position said air valve in accordance with air flow through said mixture conduit, means connecting said metering rods to said air valve to support and position said metering rods whereby fuel fiow is controlled in accordance with air flow, and control means adapted to prevent fuel flow through said power metering orifice when the pressure in said mixture conduit downstream of said throttle valve is below a predetermined value.

6. The carburetor of claim 5 wherein said control means comprises an air bleed adapted to increase the pressure at said power metering orifice to prevent fuel flow therethrough and valve means permitting air fiow through said air bleed when the pressure in said mixture conduit downstream of said throttle valve is below said predetermined value.

7. An internal combustion engine carburetor comprising a downdraft mixture conduit; a throttle valve in said mixture conduit; a fuel delivery system including a fuel bowl, a nozzle extending downwardly into said mixture conduit and having a discharge end centered above said throttle valve, and passage means connecting said nozzle and said fuel bowl; and a metering system including a fuel metering orifice in the discharge end of said nozzle, a metering rod in said mixture conduit associated with said orifice to vary the effective area thereof and control fuel fiow therethrough, an air valve rotatably disposed in said mixture conduit, means to position said air valve in accordance with air flow through said mixture conduit, a support member movable with said air valve and secured at one end to said air valve and at the other end to said metering rod to support and position said metering rod whereby fuel flow is controlled in accordance with air flow, and means for adjusting said other end of said support member relative to said air valve whereby said metering rod may be properly positioned relative to said metering orifice.

References Cited UNITED STATES PATENTS 1,010,066 11/1911 Newcomb 261-50 1,179,278

Renner 261-50 X Mock 261-50 Hess 261-50 Arnold 261-50 X Kolbe et a1 261-50 Mick 261-50 X Mick 261-50 X Tub-b 261-50 X Hill 261-50 X FOREIGN PATENTS France.

HARRY B. THORNTON, Primary Examiner.

4/1916 Carithers 261-6-5 15 T. R. MILES, Assistant Examiner. 

1. AN INTERNAL COMBUSTION ENGINE CARBURETOR COMPRISING A DOWNDRAFT MIXTURE CONDUIT, A THROTTLE VALVE PIVOTALLY DISPOSED IN SAID MIXTURE CONDUIT AND HAVING A RECESS IN THE DOWNSTREAM EDGE THEREOF TO PERMIT FLOW OF AN IDLING AIR-FUEL MIXTURE WHEN SAID THROTTLE VALVE IS CLOSED, A DOWNWARDLY INCLINED FUEL DELIVERY NOZZLE EXTENDING INTO SAID MIXTURE CONDUIT AND HAVING A DISCHARGE END CENTERED ABOVE SAID THROTTLE VALVE, FUEL DELIVERY PASSAGE MEANS CONNECTED TO SAID NOZZLE TO SUPPLY FUEL THERETO, A FUEL METERING ORIFICE IN THE DISCHARGE END OF SAID NOZZLE, A METERING ROD IN SAID MIXTURE CONDUIT ASSOCIATED WITH SAID ORIFICE TO VARY THE EFFECTIVE AREA THEREOF AND CONTROL FUEL 